P2P: Clear go_dev_addr for group started events if it is not known

Better make sure the address value included in the event message gets
cleared in case the GO Device Address is not known for some reason.
Previously, this could potentially have been some random data from
stack should we ever hit the case where wpa_s->current_ssid is not
set (which should not really happen in normal use cases).

wpa_supplicant/p2p_supplicant.c

@@ -494,6 +494,7 @@ static void wpas_group_formation_completed(struct wpa_supplicant *wpa_s,
 		ssid_txt = "";
 		client = wpa_s->p2p_group_interface ==
 			P2P_GROUP_INTERFACE_CLIENT;
+		os_memset(go_dev_addr, 0, ETH_ALEN);
 	}
 
 	wpa_s->show_group_started = 0;